The present invention relates to a system and method for sterilizing a food packaging area, such as a food packaging clean room, by introducing a sterilizing agent into the atmosphere and contacting surfaces in the area with the sterilizing agent.
Typically, food and beverage products are packaged by high-speed automated filling and packaging machines in a variety of different containers, such as bottles, cartons, boxes, cans, etc. It is advantageous and necessary in some cases, depending upon various factors, including for example, the type of food being packaged and the type of package, for the atmosphere surrounding the food packaging machines as well as various surfaces in the area to be sterilized prior to processing the food or beverage. For example, in processes for manufacturing ultimately shelf-stable products not subjected to undue heat, cold fill processes may require certain sterility.
The level of sterility can be measured in terms of classes which represent the number of particles per cubic meter. For example, cold filling certain preservative-free non-carbonated liquid beverages at temperatures of 120xc2x0 F. or less into a bottle or other container may require such processing to occur in an area of Class 100 which signifies a maximum of 100 particles greater than 0.5 microns in size per cubic foot of air. Without such sterility, the end product may have a shorter shelf life or fail to meet certain Food and Drug Administration requirements. Additionally, sterilization of the atmosphere and surfaces in the area prior to the processing and packaging of foods and beverages, typically along with certain manufacturing practices, may eliminate the need to sterilize such foods and beverages post packaging. A closed environment, such as a clean room, is often used to minimize potential contamination and to substantially maintain a desired sterile environment level once it has been obtained.
Sterilizing the food processing or packaging machines and the surrounding area causes destruction of microorganisms, including bacteria and certain types of spores. This, in turn, minimizes the risk of contamination of the food product and the spoilage rate of the food product, among other things. A need exists for an effective method of sterilizing a large area including food processing or food packaging machinery. As used herein, xe2x80x9csterilizationxe2x80x9d does not necessarily mean complete elimination of microorganisms, and as known to those skilled in the art, there are levels of sterilization (such as numbers of microorganisms in the atmosphere per cubic volume).
It is known to manually apply liquid sterilizing agents and solutions on exposed surfaces, such as on food packaging equipment and to the floor surrounding the food packaging equipment. For example, this has been achieved by application through a hose or mop directly on the desired equipment or surface. However, such a method is time and labor intensive and cannot ensure that either the surrounding atmosphere or nonexposed surfaces of the equipment have been sterilized.
A need exists for a less labor intensive method for sterilizing a food packaging area that is reliable and easily repeatable. A need exists for a method for sterilizing a food packaging area that is less time consuming. A need also exists for a precise method of obtaining a desired level of sterility in the atmosphere and all surfaces of food packaging equipment and the room containing that equipment. Merely applying a liquid sterilizing agent to equipment does not provide uniform exposure to all areas of the food packaging equipment and the surrounding atmosphere of the room, such as in a clean room, for example. A need exists to sterilize the nonexposed surfaces and the atmosphere in the room, and to minimize the waste of the sterilizing agent during the sterilization process.
In accordance with one aspect of the present invention, a method of sterilizing a food packaging area or room is provided that is especially suited for automation. This method comprises introducing a sterilizing agent into the atmosphere of the food packaging area or room to create an aerosol suspension containing the sterilizing agent and distributing the atmospheric aerosol suspension for a sufficient time and in a sufficient concentration to reduce the microorganism concentration in the atmosphere to desired levels and on the surfaces in the area that are to be sterilized. Typically, the desired level of sterility is to achieve sterilization in the area. The sterilizing agent is preferably contained in an aerosol suspension and condenses on various surfaces. By xe2x80x9caerosolxe2x80x9d, applicant means a suspension of liquid particles in the atmosphere, which particles may be in the colloidal size range (typically the colloidal size range is about 1 millimicron to about 1 micron), such as a gas, fog, mist, or fine spray or droplet.
For purposes of the present invention, xe2x80x9csurface(s)xe2x80x9d refers to the surface(s) of the walls, floor, ceiling, food processing equipment and any other thing present in the area or room that is exposed to the atmosphere of the area or room (i.e., air in the room contacts the surface of the walls and floor), the surface of which is to be sterilized. For purposes of the present invention, xe2x80x9cexposed surface(s)xe2x80x9d refer to any surface(s) that are readily accessible to direct spraying. For purposes of the present invention, xe2x80x9cnonexposed surface(s)xe2x80x9d refers to any surface(s) which are not readily accessible to direct spraying. For example, a box with spaced apart slats would contain exposed surfaces on the outside of the box and nonexposed surfaces which are inside the slats on the box yet still open to the atmosphere. It should be noted that the box in this example may contain parts which are neither exposed surfaces nor nonexposed surfaces if interior portions are completely isolated from the atmosphere. A vented enclosure for equipment may have exterior surfaces that are xe2x80x9cexposedxe2x80x9d and interior surfaces that are unexposed but open to the atmosphere and hence a xe2x80x9cnonexposed surfacexe2x80x9d in accordance with the invention. Similarly, a surface such as the interior of an incandescent bulb or cathode ray tube is neither an xe2x80x9cexposed surfacexe2x80x9d nor a xe2x80x9cnonexposed surfacexe2x80x9d and for purposes of the invention is a xe2x80x9cclosed surfacexe2x80x9d (i.e., a surface that is not exposed to the atmosphere). The present invention is not applicable to such closed surfaces.
In accordance with the present invention, the sterilizing agent may be introduced directly into the atmosphere as an aerosol suspension, preferably in the form of small droplets or a fog that condense on a surface (and are readily evaporable) to react with and/or kill microorganisms. While not wishing to be bound by theory, it is believed that sterilizing agent reacts with microorganisms when the sterilizing agent condenses on a surface, and may also react by contacting the microorganisms in the atmosphere without condensing. Preferably, the aerosol suspension condenses on all or substantially all (or as otherwise desired or needed) of the exposed surfaces to be sterilized in the food packaging area or room. The sterilizing agent is distributed throughout the area to ensure that the atmosphere and substantially all of the exposed and nonexposed surfaces are sterilized to a desired level. No circulation is accomplished in the atmosphere in the area or room to maintain high concentration of the sterilizing agent. After the sterilizing agent is present for at least a sufficient period of time to accomplish the desired degree of sterilization, the sterilizing agent may be removed from the area, leaving a resulting atmosphere and surfaces that have a sufficient sterility for a given purpose. Generally, removal of the sterilizing agent to some threshold level is necessary prior to unprotected personnel entering the area. This method can provide for more precise control over the sterility of the room than the prior art.
In accordance with another aspect of the invention, the sterilizing agent is a liquid sterilizing agent that is evaporable without leaving any residue or any substantial residue. One such sterilizing agent is known as Oxonia(trademark), which is an aqueous mixture of hydrogen peroxide, peracetic acid and inert ingredients. The sterilizing agent can be diluted as desired with an appropriate carrier liquid, such as water.
In accordance with another aspect of the invention, atmospheric conditions in the area or room to be sterilized are controlled such that the sterilizing agent, after introduction into the area or room, condenses on surfaces, including on exposed and unexposed surfaces, in the area or room to be treated.
In accordance with another aspect of the present invention, an automated sterilization system is provided that can practice the foregoing sterilization methods and eliminates the need for manual application of the sterilizing agent. Such a system can be more economical, reliable and repeatable than a manual system.
In accordance with another aspect of the present invention, the method of sterilization may be operated in a cold filling liquid product filling operation.